Roadway dividers and barriers acting only on the wheels and the steering of the motor vehicle have been developed, since automobile body active guides suffer from obvious disadvantages. When these are rigid, for example steel rails or concrete walls, then deformation and considerable damage of the impacting parts of the motor vehicle occurs under high decelerations and uncontrolled deflection angles. Flexible catch devices (wire nets and ropes) require a large amount of space with their necessary effective depth. Sometimes too little protection is provided against penetration and the repair and maintenance costs are high. Semirigid guides (aluminum or steel sheet profile guard rails) require less space and decelerate vehicles less abruptly, but they generate high repair costs for the motor vehicle and the guard rail. For large kinetic energies, the penetration resistance is also too low. Also guides acting both on the wheels and steering as well as on the automobile body are not satisfactory. Such structures have been developed in the United States and have been applied worldwide (New Jersey profile, MB 5). They provide an inclined rising base and then a nearly vertical concrete wall of a height of about 1 m. The wheels near the barrier run initially up and are lifted thereby producing an overturning moment. Only then can the automobile body parts contact the wall reflectively. This problem has never been satisfactorily overcome nor can damage to the vehicle be minimized.
Thus, there is the desire for employing guides which act solely on guides have hardly ever been employed, since it has not been possible in the past to provide a construction which met the following requirements:
1. The resulting redirecting forces and therewith the injury risk of the passengers of an impacting vehicle should be kept as low as possible,
2. the impacting vehicle should not be damaged at all or the damage should be kept low,
3. a damaging of the guide by the impact of the vehicle should be prevented,
4. crossing, jumping over or sideways rolling over should be reliably prevented,
5. the skidding off vehicle should be able to be guided with operable steering and if possible without uncontrolled deflection into the lane,
6. this redirecting should be effected in the same way for both rolling and skidding vehicles, and
7. the barrier height and width should be as low as possible should be provided for widespread use.
For example, in a publication by Dunlap in Highway, Res. Rch. 460,1973 page 3 several profiles are described, which were subjected to a test series in 1953 in California. These profiles have in each case a total height of at most 35 cm and do not act on the automobile body. They can have a simple outwardly inclined bevelled surface which has been found to be substantially useless, since only in few cases could they prevent a passing over the upper edge by the vehicle. If they are provided on their upper edge with a deflecting strip protruding against the lane, then their effectiveness is much higher. Damage to the wheels and wheel mountings however occurs even at low velocities, since the provision also at low velocities and impact angles results in a hard impact of the rim.
In a publication by Jehu in Traffic Engineering and control, Vol. 5, Nr. 9 Jan. 1964 there is described a traffic guide device in the form of the Belgian drip edge stone (Trief-Randstein), which corresponds to the barrier already described and wherein correspondingly a substantially vertical lower edge surface is situated immediately in front of an upper deflection strip. This edge surface however reaches so far upwards, that it does not act on the tire only, but abruptly acts on the rim itself. This corresponds to a repositioning of the deflection strip according to the California profiles downward, results in large overturning moments and correspondingly poor experimental results according to the presentation by Dunlap cited above. If the vehicle rided above the lower edge surface of the drip edge stone, then it does not receive at the following, slightly inclined bevelled surface a substantial influence towards a guiding back onto the lane so that also the steep surface disposed behind this bevelled surface and hardly protruding has little effect.
Another guide has been developed in Sweden (Tri-Bloc, see for example VDI-Nachrichten, Nr. 23, June 8, 1979) and acts only on the wheels and the steering. It employs two concavely curved and prismatically shaped faces of 0.8 to 1 m height, which employ without automobile body contact the steering geometry of a running up wheel for the slow redirection to the travel lane. Driving experiments in fact have shown poor results for rolling vehicles at low impact angles. Experiments with larger impact angles or with skidding processes, respectively, are not known; based on the overturning edge close to the ground and a lacking deflecting upper edge a jumping over with catapult effect or a rolling over, respectively, of the vehicle onto the opposite side should not be prevented. In any case this barrier does not meet the requirement of low height and small width. It is therefore not only expensive, but also an optical barrier, which according to experience reduces the road width used by the traffic.